After only three days of the Candidates tournament in London, the possible identity of Viswanathan Anand's next title challenger has already been reduced from eight to six names.

Predicting the result of a marathon by looking at the leading runners after only 5 miles is hardly reliable, but in London the two oldest players in the field, 44-year-olds Vassily Ivanchuk and Boris Gelfand, may already be out of contention, having lost two consecutive games and trailing the rest of the field by a point. Even though Ivanchuk and Gelfand may recover ground, it is too much to ask of the veterans to then maintain the challenge for first place over a grueling 14 round tournament.

"It's a long tournament," offered both Kramnik and Carlsen as some sort of explanation for their insipid second round draw. When an impudent journalist suggested that the 28 round Candidates tournament of sixty years earlier in Zurich might have been tougher, Kramnik reacted sharply; "It is ten time harder now than it was in 1953 - computers have changed everything. In 1953 they prepared for just one or two hours before a game, we are preparing almost non-stop. Also in 1953 there were more or less only two openings played - the Nimzo-Indian and the King's Indian but now the players are much more flexible. We also have to play up to seven hours, whereas in 1953 I had the feeling that some of the draws were prearranged."

As the players went into the first rest day on Monday, world number three Levon Aronian led the field - “a pleasant surprise and more than I would have hoped for” said the Armenian.

Aronian is half a point clear of tournament favourite Magnus Carlsen and a fit and in-form Peter Svidler. Half a point further back lie the tournament's drawing masters Vladimir Kramnik and Alexander Grischuk, plus the less stable Teimour Radjabov.

The raw scores, however, show little of the drama which has unfolded at IET, with the chess clock taking a starring role.

Despite slightly disappointing crowds – the $50 admission fee keeping attendances on the weekend days to fewer than 120 – the tournament has already seen extraordinary drama, most notably in the games of Ivanchuk.

In all three games Ivanchuk found himself with less than 10 seconds for his last half dozen moves, and in two of those games Ivanchuk lost on time.

Ivanchuk's third round game was simply disastrous...

London Candidates 2013

White: V.Ivanchuk

Black: L.Aronian

Position after White's 25th move

From a standard Torre Attack, Ivanchuk had launched an early kingside assault, but it took him an extraordinary amount of time and within 15 moves he was an hour behind Aronian on the clock.

By move 20 Ivanchuk was down to two and a half minutes to reach move 40 and five moves later his clock and position were not looking good. Aronian takes up the story...

"By now Vassily had about 20 seconds left and I knew that I was going to win on time. My next move was simply to confuse him and gain a few seconds.

“Normally time trouble for guys like Grischuk and Ivanchuk is nothing - usually Vassily plays very well in time trouble. But this is [a Candidates tournament] and the pressure can get to you."

25...a6!!??

A brilliantly irrelevant move. After the game Aronian was shown the sacrifice he had missed; 25...Bxd4!! 26.cxd4 Rxb4 when Black has, according to the computer oracles, a winning attack. Yet he was far from convinced that his confusion strategy was wrong - pointing out that a line like this could give Ivanchuk too many forced replies and therefore a chance to reach the time control.

26.Qe3 Qg4 27.g3 Rb5 28.Rxa6 Rxa6 29.Nxa6 e5!?

"I got too excited," admitted Aronian, "but he had only 5 seconds to go so I forgive myself!"

30.dxe5 Bxe4

31.c4!

After he played this move, which left him with just four seconds on the clock, Ivanchuk sank back into his chair with a smile on his face. The Ukrainian explained "31.c4 was a beautiful move, but unfortunately I realised that even if he would start to give me material on every move I would still lose on time!"

31...Rb6 32.Qxb6 Qf3 33.Qf2 Qa3 0-1

Here Ivanchuk lost on time as he was playing 34.Nc5. At the press conference Aronian showed a line which seemed to be winning but Ivanchuk was not worried - "Sure, the position can be analysed, but my time was gone."

Curiously Ivanchuk seemed most upset by his time management in the game he drew in round one against Grischuk; “The last two games were complicated [so getting short of time is understandable] but in the first game, [having played] so many moves of theory, that is...” and a wave of the arm and a sigh indicated that Ivanchuk was giving himself a serious reprimand.

Aronian's playing the man as much as the board had success in the second round as well.

London Candidates

White: L.Aronian

Black: B.Gelfand

Position after Black's 24th move

Gelfand is a pawn down but his bishop pair gives him excellent drawing chances. Black has just played 24...Bf6-d8 and Aronian realised that Gelfand was probably preparing 25...Rc8 so...

"After he played this move I was thinking - which move can I play to provoke 25...Rc8? I looked at 25.Rc2 and 25.Rc3 but then realised that b4-b5 would be very important in some lines and played..."

25.b4! Rc8?

Obvious but fatal. On 25...Bb6 Gelfand had reason to fear 26.d5! so practically 25...Bd5 was best, though that would mean Gelfand abandoning his idea of exchanging rooks.

26.Bh6+!!

The proverbial bolt from the blue.

26...Kg8

26...Kxh6 27.Rxc8 Bxc8 28.Nxf7+ is hopeless, while 26...Kf6 27.Bg5+! Kxg5 28.Nxf7+ Kf4 would be rather messy if White had to swap rooks, but instead he can play 29.g3+! Kf3 30.Re1! and mate next move. "I hadn't actually seen this!" Aronian confessed after the game.

The best defence was 26...Kf6 27.Bg5+ Kxg5 28.Nxf7+ Kf6 29.Rxc8 Bxc8 30.Nxd8 e5 but then 31.d5! a6 32.Nc6 Bb7 33.Kf1 seems to be winning for White in all lines.

27.Rxc8 Bxc8 28.Nc6 Bf6 29.b5! Bd7

30.g4!

The crusher that Aronian had seen on move 25.

30...g5

After 30...a6 31.g5 axb5 32.Nb8 wins a piece.

31.h4! gxh4 32.g5 Bxc6 33.bxc6 Bd8 34.Kg2 Bc7 35.Kh3 1–0

Photo Cathy Rogers

So while Aronian began to break away from the field with his tactical tricks, his first round opponent and top seed Carlsen needed to grind hard to stay in touch.

London Candidates

White: B.Gelfand

Black: M.Carlsen

Position after Black's 46th move

In typical style, Carlsen had first neutralised Gelfand's attacking efforts, transposed to a slightly better endgame - “drawn, but with some practical possibilities for Black” said the Norwegian - and now has reached an unbalanced position where his queenside pawns are looking dangerous.]

47.Qxd8+?

"I miscalculated," admitted Gelfand who thought for 20 minutes over this exchange. "If I play 47.Qb7 then 47...Qd3 is annoying, while after; 47.Qc6 b3 I don't see what White can do."

Gelfand was correct that 47.Qb7 Qd3 is bad for White but he was unduly pessimistic in his second line; after 47.Qc6 b3 48.Bc1! White has slowed down the pawns and keeps drawing chances.

47...Nxd8 48.Kf3 a4 49.Ke4 Nc6 50.Bc1

"When I exchanged queens I thought I was drawing with 50.Kd5 but of course after 50...a3 51.Kxc6 b3 I cannot stop the pawns," said Gelfand.

50...Na5 51.Bd2 b3 52.Kd3 Nc4! 53.Bc3 a3 54.g4 Kh7! 55.g5

55...Kg6!

"Black is in zugzwang," declared ICC commentator Jon Speelman who a few moves earlier had wondered whether Carlsen had missed his way. "I should never have doubted Magnus!"

56.Bd4

The only waiting move, but now Black has...

56...b2 57.Kc2 Nd2! 0–1

Photo Cathy Rogers

“In Wijk aan Zee I didn't win until the third round and then I finished on +7, so I expect that will happen here as well,” said Carlsen tongue-in-cheek after the game.

Peter Svidler dragged himself away from the dramatic England v New Zealand cricket Test Match ・ a contest where the last 10 hours of play were aborted due to rain ・ to match Carlsen by also winning his third round game.

London Candidates

White:P.Svidler

Black:T.Radjabov

Position after Black's 40th move

Radjabov had beaten Ivanchuk (on time) in the second round but in this game found the shoe on the other foot, with a bad position and needing to make four moves in five seconds to avoid a time forfeit. Not only did the Azeri safely reach the time control, but his last move, 40...Rd1-d4! sets a vicious trap...

41.Bxd6!

Avoiding 41.g3? Rxc4+ 42.Kxc4 d5+!, winning the rook on g6.

"I was very lucky that this was after move 40," admitted Svidler. "I had planned to play 41.g3, though I think that I would have spotted the problem even if I hadn't been given an additional hour [thinking time]."

41...Rxh4 42.Ne5+ Kc8 43.Rg8+ Kb7 44.Bxc5

The rest of the game needs some precision from Svidler but "If I cannot win this position then I should not be here!"

44...Re6 45.Rg7+ Kc8

On 45...Ka6 46.Bd4 Kb5 47.Rb7+ keeps the Black king in a net.

46.Nc4 Rg4

47.Nd6+! Kb8 48.Rb7+! Ka8 49.Rd7! Rg8 50.Nc4 Rxg2 51.Bd6!

51.Nb6+?! Rxb6 52.Bxb6 is still winning for White, but the endgame, even without the h5 pawn, is a tricky technical task.

51...Rxd6 52.Nxd6 h4 53.Rh7Rh2 54.Kb4 h3 55.Ka5 1–0

So what conclusions can be drawn from the tournament to date?

Carlsen and Aronian are both capable of racking up big plus scores, so we could be in for an epic race.

The three Russians, having already played amongst themselves, are well set to challenge the leader, while Radjabov is playing sharply enough to win a lot of games.

A comparison could be made with the San Luis FIDE Tournament World Championship in 2005 played in a similar format. In that tournament Anand and Topalov raced to 2.5/3 but Topalov then won four straight games in rounds 4 to 7 and, with Anand unable to keep pace, was able to coast to the finish.

The world body FIDE's gamble in handing World Championship chess to the AGON company for a decade has seen its first big test in London, and AGON deserves at least a good pass mark.

The organizers have done the big things well but foundered on details. The Institute of Technology and Engineering building is an outstanding venue - easily accessible in the centre of London - and the 300 seat arena would be ideal were it not for a weird set of wooden barriers which prevents large areas of the hall from seeing all four games. Similarly, the Samsung tablets provided to the audience to watch the games and listen to the commentary, is a great innovation. Sadly there are only about 40 tablets provided, so many spectators miss out.

The special World Championship chess sets have caused only a few concerns - "I was worried that in time trouble, if my king and queen were next to each other, I would move the wrong piece!" said Ivanchuk.)

The white logo on the board, which had been a source of complaint at the technical meeting, was covered up before the first round started.

The change made to the board is just one indication that AGON chief Andrew Paulson, whose enthusiastic presence seems to be everywhere all the time; before, during and after the rounds is happy to make improvements as the event progresses.

The one necessary change it is probably too late to make is to the design of the electronic display boards, which are universally disliked. The AGON broadcast has some attractive new features, including instant assessments of various aspects of the game, but the colours used - white and red and grey - are a most unfortunate choice. (One unhappy colour-blind spectator complained that he could not see the red pieces on dark squares at all.) Add to that the difficulty in distinguishing between rooks and queens, and the result is a display that is both difficult to follow and hard to look at for any length of time.